<?php

/**
 * @user magein
 * @date 2024/2/26 10:15
 */

namespace magein\utils;

/**
 *数据可逆加密
 */
class DataSecurity
{
    /**
     * @var string
     */
    protected string $key = 'data_security';

    /**
     * 加密
     * @param string $data
     * @param string|null $key
     * @return string
     */
    public function encrypt(string $data, string $key = null): string
    {
        $key = $key ?: $this->key;
        $char = '';
        $str = '';
        $key = md5($key);
        $x = 0;
        $len = strlen($data);
        $l = strlen($key);
        for ($i = 0; $i < $len; $i++) {
            if ($x == $l) {
                $x = 0;
            }
            $char .= $key[$x];
            $x++;
        }
        for ($i = 0; $i < $len; $i++) {
            $str .= chr(ord($data[$i]) + (ord($char[$i])) % 256);
        }
        return base64_encode($str);
    }

    /**
     * 解密
     * @param string $data
     * @param string|null $key
     * @return string
     */
    public function decrypt(string $data, string $key = null): string
    {
        $key = $key ?: $this->key;
        $key = md5($key);
        $x = 0;
        $data = base64_decode($data);
        $len = strlen($data);
        $l = strlen($key);
        $char = '';
        $str = '';
        for ($i = 0; $i < $len; $i++) {
            if ($x == $l) {
                $x = 0;
            }
            $char .= substr($key, $x, 1);
            $x++;
        }
        for ($i = 0; $i < $len; $i++) {
            if (ord(substr($data, $i, 1)) < ord(substr($char, $i, 1))) {
                $str .= chr((ord(substr($data, $i, 1)) + 256) - ord(substr($char, $i, 1)));
            } else {
                $str .= chr(ord(substr($data, $i, 1)) - ord(substr($char, $i, 1)));
            }
        }
        return $str;
    }
}